Data communication systems have been under development for many years. Many communication systems employ error-correcting codes, such as LDPC (Low Density Parity Check) codes, to improve reliability and efficiency.
There are many known algorithms for iterative decoding of LDPC codes. A generic message-passing algorithm, called “sum-product algorithm”, performs iterative decoding through exchanging messages between nodes of a factor graph along the edges of the graph and updating these messages at the nodes based on the incoming messages. Details about sum-product algorithm can be found in publications, such as: R. G. Gallager, “Low-density parity-check codes,” Ph.D. dissertation, Department of Electrical Engineering, M.I.T., Cambridge, Mass., July 1963; F. R. Kschischang, B. J. Frey, H. A. Loeliger, “Factor Graphs and the Sum-Product Algorithm,” IEEE Trans. on Information Theory, Volume IT-47, No. 2, February 2001; and European Telecommunications Standards Institute (ETSI) EN 302 307, Digital Video Broadcasting (DVB), V1.1.1 (2005-03).
To improve performance or to reduce complexity, some modified algorithms have been proposed, such as, min-sum algorithm and lambda-min algorithm described in: Marc P. C. Fossorier, “Reduced Complexity Iterative Decoding of Low-Density Parity Check Codes Based on Belief Propagation” published in IEEE Transactions on Communications, vol. 47, No. 5, May 1999; F. Guilloud, E. Boutillon, and J. Danger, “Lambda-Min Decoding Algorithm of Regular and Irregular LDPC Codes,” In Proc. 3rd International Symposium on Turbo Codes & Related Topics, pages 451-454, Brest, France, September 2003; and U.S. Patent Application Publication No. 2005/0138519 by Boutillon et al.
The above mentioned references are incorporated herein by references.